Van's Air Force
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governor response
- Thread starter jimgreen
- Start date
Steve Barnes
Well Known Member
Over shoot
I am sure you are not doing this, but just in case. On the first take off of the day you need to cycle the prop to get warm oil in it or you will get an over speed. Don't ask me how I know.
Steve The Builders Coach
I am sure you are not doing this, but just in case. On the first take off of the day you need to cycle the prop to get warm oil in it or you will get an over speed. Don't ask me how I know.
Steve The Builders Coach
Captain_John
Well Known Member
Might not be the governor. Might be the prop hub.
I have the same setup but am not flying yet.
A wise man once told me that if what you are describing happens, it could be a prop hub adjustment.
If someone here knows more and could lead the discussion in that direction, it could solve your problem. If not, i could talk to the guy who told me about it.
CJ
I have the same setup but am not flying yet.
A wise man once told me that if what you are describing happens, it could be a prop hub adjustment.
If someone here knows more and could lead the discussion in that direction, it could solve your problem. If not, i could talk to the guy who told me about it.
CJ
hydroguy2
Well Known Member
Might not be the governor. Might be the prop hub.
I have the same setup but am not flying yet.
A wise man once told me that if what you are describing happens, it could be a prop hub adjustment.
If someone here knows more and could lead the discussion in that direction, it could solve your problem. If not, i could talk to the guy who told me about it.
I'm interested in your wise man. I've asked several folks and the consensus around here is "normal". But I can overspeed my prop if I jam the throttle forward on any start.
Captain_John
Well Known Member
DOH!!! The wise man was certainly not me!!!
I seemingly cannot read. I saw WW but thought Hartzell.
Anyways... I called Mitch and he says that on a HARTZELL the Minimum Pitch Blade Angle is adjusted by the allen screw in the center of the hum. a half turn in usually prevents this overspeed from occurring.
Now, I am not sure about the WW but there must be a similar setting for min pitch, no???
He also went on to say that the prop guv cannot keep up with the instant surge that you see on takeoff and that is why Hartzell has this adjustment.
Les, am I right? You know this stuff. Can you confirm or deny it for us Hartzell guys?
WW guys, let us know if yours is similar.
CJ
I seemingly cannot read. I saw WW but thought Hartzell.
Anyways... I called Mitch and he says that on a HARTZELL the Minimum Pitch Blade Angle is adjusted by the allen screw in the center of the hum. a half turn in usually prevents this overspeed from occurring.
Now, I am not sure about the WW but there must be a similar setting for min pitch, no???
He also went on to say that the prop guv cannot keep up with the instant surge that you see on takeoff and that is why Hartzell has this adjustment.
Les, am I right? You know this stuff. Can you confirm or deny it for us Hartzell guys?
WW guys, let us know if yours is similar.
CJLow Pitch Stop
Yes, setting the low pitch stop properly is the best way to prevent or minimize RPM overshoots during max power static/takeoff conditions. I normally set the low pitch stop for 25-50 RPM below rated RPM during a max power static run-up. I do this by starting at a high angle and running a series of decreasing blade angles to develop a relationship between blade angle and RPM. This allows me to pick an angle that includes the factory assembly tolerance on the low side. This should minimize or prevent any RPM overshoots during static/initial takeoff throttle slams. It will do nothing for you in flight since the prop is off the low pitch stop at ~40 kts.
I realize this would be difficult for someone that doesn't have the tools to measure blade angle, so I would recommend you first confirm the governor high RPM stop is set properly in flight, say 2700. Then I would start increasing the low pitch stop setting during a series of max power run-ups until you see it drop just below the max rating. I understand max power run-ups on lightweight RVs carries some risk so you might want to do this iterative process by noting RPM overshoots during normal takeoffs. You can increase the low pitch setting a little each time until the overshoots diminish or go away entirely.
Yes, ambient conditions will affect your results. Do this on a low/cold day and you are likely to set the angle a little high; on a high/hot day you will probably be a little low. If you are turbocharged it gets more complicated...
The low pitch stop adjustment on Hartzell props is very easy. The procedure is in the Owner's Manual 115N. I'm not familiar with how the WW low pitch is set or even if it can be adjusted on-wing?
The low inertia of composite props increases the likelihood of overshoots; they spin-up faster making it harder for the governor to catch it before exceeding the high RPM setting.
I have an example chart I can share once I figure out how to post/attach it to a message.
Les Doud
Hartzell Propeller
Yes, setting the low pitch stop properly is the best way to prevent or minimize RPM overshoots during max power static/takeoff conditions. I normally set the low pitch stop for 25-50 RPM below rated RPM during a max power static run-up. I do this by starting at a high angle and running a series of decreasing blade angles to develop a relationship between blade angle and RPM. This allows me to pick an angle that includes the factory assembly tolerance on the low side. This should minimize or prevent any RPM overshoots during static/initial takeoff throttle slams. It will do nothing for you in flight since the prop is off the low pitch stop at ~40 kts.
I realize this would be difficult for someone that doesn't have the tools to measure blade angle, so I would recommend you first confirm the governor high RPM stop is set properly in flight, say 2700. Then I would start increasing the low pitch stop setting during a series of max power run-ups until you see it drop just below the max rating. I understand max power run-ups on lightweight RVs carries some risk so you might want to do this iterative process by noting RPM overshoots during normal takeoffs. You can increase the low pitch setting a little each time until the overshoots diminish or go away entirely.
Yes, ambient conditions will affect your results. Do this on a low/cold day and you are likely to set the angle a little high; on a high/hot day you will probably be a little low. If you are turbocharged it gets more complicated...
The low pitch stop adjustment on Hartzell props is very easy. The procedure is in the Owner's Manual 115N. I'm not familiar with how the WW low pitch is set or even if it can be adjusted on-wing?
The low inertia of composite props increases the likelihood of overshoots; they spin-up faster making it harder for the governor to catch it before exceeding the high RPM setting.
I have an example chart I can share once I figure out how to post/attach it to a message.
Les Doud
Hartzell Propeller
Captain_John
Well Known Member
Thanks Les!
Guys, sorry about the confusion about the brands.
Does your hub have the same thing?
CJ
Guys, sorry about the confusion about the brands.
Does your hub have the same thing?
CJ
IMHO, The proper way to set up a prop is to have the fine stop regulate down to 2700-2800 and then do the rest with the gov. We had to change to low pitch stop on our WW 200RV. If you need to do that contact them for a set of washers. With the McCauley hub you have to pull the dome and adjust the fine pitch travel by adding washers under a snap ring. You need 2 people to help, one on each blade and one to pull the snap ring and add washers. We ended up having to add a total of 5 washers, 0.030 inches thick each. I tried to measure difference but due tou our symptoms was unable. We started out by being able to drive the prop to 2890 with about 60-70% throttle on the ground. Now we can go to about 2850 with full throttle. We first added 3 per WW recommendation, and then later added the other 2, which I roughly measured as about 1 deg (2 washers). We adjusted the rest with the prop gov travel stop.
Couple of notes. One, I think the lack of mass of the composite blades makes RPM changes more abrupt. I mean if you slam the throttle forward you can overspeed before the gov has time to adjust back down. Two, I hear all the talk of prop really slowing you down when you pull the power in idle and oil pressure drops, but with our stop adjustment we don't get any drastic or noticable braking. That makes me think, that there are a lot of props that should have the fine stops adjusted.
Couple of notes. One, I think the lack of mass of the composite blades makes RPM changes more abrupt. I mean if you slam the throttle forward you can overspeed before the gov has time to adjust back down. Two, I hear all the talk of prop really slowing you down when you pull the power in idle and oil pressure drops, but with our stop adjustment we don't get any drastic or noticable braking. That makes me think, that there are a lot of props that should have the fine stops adjusted.
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RVjim
Well Known Member
2600 to 2650 static RPM recommended
Hi Jim,
The light weight blades on the whirlwind (and MT) propeller allow the engine to respond almost directly to the throttle position. If the throttle is set to a position that gives 1200 RPM, when the engine starts it will be running at 1200 RPM.
The propeller low pitch stop should be set give a static RPM of between 2600 to 2650 RPM.
This is not my opinion. This is a safety of flight issue.
The governor low RPM setting controls the engine RPM after the propeller blades come off of the propeller low pitch stops. This would happen very early in the takeoff roll.
Jim Ayers
MT Propeller distributor
FAA Propeller Repair Station # [FONT='Arial','sans-serif']LDSR535X[/FONT]
Hi Jim,
The light weight blades on the whirlwind (and MT) propeller allow the engine to respond almost directly to the throttle position. If the throttle is set to a position that gives 1200 RPM, when the engine starts it will be running at 1200 RPM.
The propeller low pitch stop should be set give a static RPM of between 2600 to 2650 RPM.
This is not my opinion. This is a safety of flight issue.
The governor low RPM setting controls the engine RPM after the propeller blades come off of the propeller low pitch stops. This would happen very early in the takeoff roll.
Jim Ayers
MT Propeller distributor
FAA Propeller Repair Station # [FONT='Arial','sans-serif']LDSR535X[/FONT]
